1985 GL1200 Limited ECU Replacement/Upgrade

[Rednaxs60]

Continuing with road trials. Lots of good tuning recommendations from the Speeduino forum. If this were a car, could have someone with me changing engine tune parameters on the fly, could do the same on the bike, but never easy doing anything extra on a bike. Have to change my tuning process to get tuning done while on the road. The engine is using a lot of fuel at this time, will be changing the VE Table cell values to compensate.

The recommended tuning procedure is to ride at a specific speed/RPM, stop, review data log. Repeat until the leanest stable cruise is found - just rich of "lean surge". Enter the AFR reading in the respective cell value, then tune ignition timing for minimum MAP.

For those of us that have never heard of this, I hadn't - wasn't looking for it either:

"Lean surge is typically related to a lean mixture (read typical factory jetting) and occurs when cruising along at steady state speeds with small throttle openings. You can actually feel the bike pull and then pause, pull and pause".

I will be doing this as a VE "block" change scenario. Will be monitoring the VE block of 56 to 90 KPa and 2000 to 4500 RPM. This is a 6 by 8 matrix.

Learning the tuning and analytic software is a challenge but getting there.

[Rednaxs60]

Have been busy with family that has put this project on hold. Lots to report. Motorcycle EFI engine tuning is purported as being similar to a car/truck, but it is different.

IMO the MAP window for engine tuning is relatively small/narrow. A motorcycle engine tends to use the same engine load range for most of the engine operation. What this means is that engine tuning at different engine loads is extremely challenging.

I have been doing road trials for several months in between other issues. More research has been done and I have found forum threads, not necessarily motorcycle, that mention the OEMs use the stoichiometric air-fuel ratio of 14.7 for idle, low speed and cruising speeds. I have applied this premise to my engine tuning and it is providing good results, it covers a wide range of engine load - 60 to 95 kPa, and RPM ranges from idle up to 3500.

The Honda CFI system is comprised of EFI components that were cobbled together and made to work, and work well. I have come to the realization that I will not be able to duplicate the Honda CFI system operation, and as such, will not be doing so.

The engine tune parameters are different. The fuel system operates at 40 PSI instead of th OEM fuel system pressure of 28 to 32 PSI. Sequential fuel and ignition, coil-on-plug (COP), and more. Mentioned these before, but a refresh is always good.

I have had to change my mindset to disregard the Honda CFI system operation and philosophy, and start with a fresh perspective for engine tuning as if this was a stand alone conversion not an upgrade. Thinking that a stand alone starting from scratch EFI install would have been easier because there is no baggage attached.

Have tried many different theories/strategies to get closer to a good engine tune. As I have mentioned there are no definitive processes/procedures available so I have tried different "roads" to try and achieve the end game. You need to be able to sift through the wealth of information available to you and determine a way ahead.

There are forum posts asking for assistance regarding pre-made VE(fuel) and spark (ignition timing) tables. The take away from this and it is mentioned in various forum posts is that any time you resort to using another persons information, you must remember this is a starting point, not the final solution.

I have read forum posts that using Tuner Studio (TS) Tune Analyze Live (let the software make changes to the VE (fuel table) should not be used initially, good suggestion. You need to get a "handle" on the engine fuel requirement - good suggestion and needed. Once you have a "handle" on the fuel requirement, calibrate the spark (ignition timing) table, then the AFR table. Easy process if you have a laptop in a car, but more challenging with a motorcycle.

This last set of road trials, I used TS Tune analyze Live to start to dial in the VE table for me. It has worked. I did three/four road trials letting the tuning software adjust/recalibrate the VE table. Started to see good results. I have now moved on and use the data collected and the data analysis software to adjust/recalibrate the VE table to suit. I have made the decision that The AFR ratios in the idle, low RPM and cruising RPM should be in the 14.0 to 14.7 AFR range. This covers a lot of the VE table for an engine load of 60 to 95 kPa, and engine Rpm range from idle to approximately 3500.

Next item I am looking at are the exhaust sounds, "burbles" these are called. This is either too much or not enough fuel in the engine cylinder(s) causing a misfire. Identifying a misfire in the data analysis software is not easy for us neophytes, and what parameters do I look at. I have been watching the RPM per second (RPM/s) data for some time and think that this is a key parameter in identifying misfires. The RPM/s is displayed as spot on, or as positive/negative value. A misfire is generally from lack of fuel, and doesn't have to be all the time or over a wide range of operation. I think that a positive RPM/s value will not result in a misfire as this should result in an engine RPM increase, whereas a negative value indicates a lack of fuel and depending on the negative value, the greater the misfire. I have noticed that these positive/negative RPM/s values are for a very short time duration in the ms range. I will be using this parameter to calibrate the VE table as well.

Lastly, before I start to incorporate some of the other tuning features, I will be calibrating the spark table (have done some small adjustments to date), advancing the ignition timing to help lean out the air-fuel mixture, and retarding to richen the air-fuel mixture. The objective with ignition timing is to have just the right amount of ignition timing such that the air-fuel mixture is completely combusted at around the 10 to 15 degree ATDC - best for performance and fuel economy. If the burn continues after this, the engine is being used as a heat sink, coolant temperature will increase and spark plug fouling can occur. If the air fuel mixture burn is completed before this, engine performance is impacted as well as fuel economy.

Looking at acceleration enrichment (AE), similar to the accelerator pump in a carburetor, for engine performance. Read that to tune the AE you have to disable when AE will start to taper off, and when it is no longer required - easily done, set these RPM parameters above the engine red-line. There are two AE profiles available, TPS or MAP based AE profiles. The main difference is the engine load parameter being used. I am using the TPS AE profile. Nice thing about being able to modify the engine tune is that I can change this profile to MAP AE, and experiment.

I'm hopeful that the engine tune will progress faster over the next couple of weeks such that I can start to use other features available.

Cheers